Geminate consonants, also known as long consonants, appear in many languages in the world, and how they contrast with their short counterparts, or singletons (e.g. /tt/ vs. /t/), is an important topic that features in most linguistics and phonology textbooks. However, neither their phonetic manifestation nor their phonological nature is fully understood, much less their cross-linguistic similarities and differences. As the first volume specifically devoted to the phonetics and phonology of geminate consonants, this book aims to bring together novel, original data and analyses concerning many individual languages in different parts of the world, to present a wide range of perspectives for the study of phonological contrasts in general by introducing various experimental (acoustic, perceptual, physiological, and electrophysiological) and non-experimental methodologies, and to discuss phonological contrasts in a wider context than is generally considered by looking also at the behaviour of geminate consonants in loanword phonology and language acquisition. Studying geminate consonants requires interdisciplinary approaches including experimental phonetics (acoustics and speech perception), theoretical phonology, speech processing, neurolinguistics, and language acquisition. Providing phonetic and phonological details about geminate consonants across languages will greatly contribute to research in these fields.